The invention relates to improvements in methods and apparatus for making reclosable bags and particularly in a form fill process wherein completed reopenable bags are formed by feeding film downwardly over a filling spout. More particularly, the invention relates to an improved manner in which completed packets or bags are formed with a reclosable zipper at the opening. A safety seal joins the edges of the bag opening in a manner to provide the sole joining means and provide an air-proof and moisture-proof seal for the bag opening and also to provide a tamper-evident means by a web between the elements of the zipper, which web must be severed or torn for access into the bag.
The art of making reclosable bags equipped with extruded plastic profile reclosable separable fastener means has experienced a long period of development as reflected in numerous patent disclosures. It has been conventional practice to extrude plastic material in tubular or sheet form with the profile separable fastener means co-extruded along and parallel to the longitudinal formation axis of the web, that is, the direction in which the web is extruded. On the other hand, prefabricated separable fastener strip means have been secured to separately formed web and with the fastener strip means extending longitudinally parallel to the longitudinal formation axis of the web. By way of example, U.S. Pat. No. Re. 29,043 is referred to as disclosing coextrusion of web and fastener means and forming the same into bag sections.
U.S. Pat. No. 3,948,705 exemplifies the technique of securing reclosable fastener strips to the plastic film parallel to the longitudinal formation axis of the web by fusion or heat seal methods.
Attachment of separable fastener strips parallel to the longitudinal formation of the axis of the web by adhesive means is exemplified in U.S. Pat. Nos. 4,372,793, 4,354,541 and 4,355,494.
U.S. Pat. No. 4,046,408 discloses separably interlockable fasteners along the edges of the plastic sheet material having generally arrow-shaped profiles, the fasteners being either integrally extruded from flat sheets or tubes of plastic film or supplied in the form of extruded strips attached to the web or film by heat sealing.
In the formation of reclosable plastic bags when the bags are used for foodstuffs and like material, it is advantageous to have the bags supplied with a tamper-evident seal which not only protects the contents from the ingress of foreign materials and contamination, but also shows if inadvertent or intentional opening has occurred prior to the bag and its contents being in the possession of the buyer. Such a protective seal if formed continuous externally of the reclosable seal rather than internally, can additionally protect the reclosable zipper elements from dust and dirt and other contaminants with a permanent protective seal located outwardly of the reclosable seal, moisture and other foreign elements cannot enter the bag and the purchaser can see that he is obtaining a previously unopened and unused bag where the contents are fully protected. This conveys a feeling of safety and comfort to the purchaser who may be concerned about someone criminally obtaining access to the bag and placing dangerous contaminants into the contents.
Examples of tamper-evident structures are shown in U.S. Pat. Nos. 2,978,769, 3,172,443, 3,685,562 and 3,780,781.
My recently issued U.S. Pat. No. 4,709,533 discloses a tube made from film in a form fill process wherein the tube has fastener strips joined to the inner surface of the film material inside of a fin seal made between the edges of the film. This method and structure while providing advantages over arrangements heretofore used, requires that sufficient film be provided to be joined outside of the fastener strips, and the joined fin seal of the film is limited to being of the weight of the film.